1. Field of the Invention
This invention relates generally to a method and an apparatus for automatically counting and stacking generally planar-shaped articles delivered to the apparatus in succession. More particularly the invention relates to a method and an apparatus for automatically counting and stacking cooked or partially cooked tortillas or similar food products into groups of a predetermined number for packaging and shipment.
2. Discussion of the Prior Art
Various article stacking methods and types of article stacking apparatus have been developed in the past. Typically the prior art devices comprise a conveyor system adapted to transport rigid articles, such as tile, brick and the like to a vertically movable platform. As the object is received on the platform, the platform is lowered to make way for the next article which is slid into position on the preceding article. After a stack of objects has been formed in this manner, a second conveyor is generally provided to carry the stack away to a shipping area. The patent to U. Walchhuter, U.S. Pat. No. 3,366,253, describes an apparatus of this general type.
Where the articles to be stacked are in the form of semirigid sheet material, such as tortillas or similar food products, special stacking problems are encountered. For reasons of sanitation as well as operational efficiency, it is essential that the product not be directly handled by the operator at any time throughout the cooking or other preparatory cycle, the stacking operation or the transfer and packing operations. The apparatus, therefore, must be highly reliable and fully automatic. Additionally, because of the lightweight, semirigid and fragile character of food products, such as tortillas, prior art stacking techniques designed for the stacking of rigid, stable, heavier weight articles have generally proved unsatisfactory.
For example, stacking methods in which the articles to be stacked must slide upon one another are unacceptable because such methods would fold, tear, abrade or otherwise damage the fragile food products.
The patents to Mitchell et al., U.S. Pat. No. 3,392,853 and to J. P. Pomara, Jr., U.S. Pat. No. 3,525,443, are illustrative of prior art apparatus used for stacking objects such as tortillas. As will become apparent from the description which follows, these devices operate in an entirely different manner from the apparatus of applicant's invention.
Additionally, as will become apparent from the description which follows, one of the principal advantages of the apparatus of the present invention over prior art counting and stacking machines is its high speed of operation. Because of the complexity and operating delay times of the object stacking mechanisms, most prior art devices are significantly limited in the number of objects which can be received from the input conveyor. For example, in devices utilizing hydraulically operated receiving pans of the type exemplified by U.S. Pat. No. 3,525,443, the frequency with which units can be received from the input conveyor for stacking is limited by the time required for the receiving pans to be moved from a receiving position to a retracted position and back to a receiving position. After a stack of the desired number of articles is completed additional time delay is built into the system to enable the stack to be transferred to the output conveyor for removal from the stacking area.
The unique design of the present apparatus virtually eliminates time delays due to operation of the article receiving and stacking mechanism of the device. The objects to be stacked are received from the input conveyor directly onto a receiving surface and are automatically aligned. When the stack is completed, the articles are expeditiously transferred to the output conveyor for removal from the stacking area by means of a novel cam and cooperating locating arm arrangement which revolves as a unit to simultaneously lower a first set of locating arms and bring the articles into engagement with the output conveyor.
Continued rotation of the unit immediately brings a second set of locating arms into position to receive articles from the input conveyor and locate them on the receiving surface. This novel construction eliminates article overshoot and permits rapid and continuous feeding of articles onto the receiving surface of the stacking mechanism.
In addition to the patents previously identified, the following patents comprise pertinent prior art known to applicant:
______________________________________ 1,661,969 - Semashko 2,606,483 - Forbes, Jr. 2,789,709 - Shields 2,825,475 - Roberts 3,014,599 - Lawrence, et al. 3,306,475 - Mays 3,291,010 - Williamson 3,205,794 - Califano, et al. 3,374,902 - Mills 3,393,645 - Mason, Jr. 3,533,517 - Heide ______________________________________